| A | B |
|---|
| anthracite | hard coal; fourth and last stage in the development of coal |
| bituminous coal | soft coal; third stage in the development of coal |
| combustion | the process of burning something |
| fossil fuel | fuel formed from the ancient remains of dead plants and animals |
| hydrocarbon | organic compound containing the elements hydrogen and carbon |
| lignite | brown coal; second stage in the development of coal |
| natural gas | flammable gas occurring naturally underground and used as fuel |
| oil (crude) | a naturally occurring, liquid hydrocarbon used for various purposes |
| peat | soft substance of decayed plant fibers; first stage in coal development |
| petrochemical | any useful substance derived from oil or natural gas |
